\documentclass{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}\rho \left(\frac{\partial \mathbf{v}}{\partial t}+\nabla_{\mathbf{v}}\mathbf{v}\right)=\rho \mathbf{f}-\nabla p +\mu\left(\Delta \mathbf{v}+\frac{1}{3}\nabla\left(\nabla\cdot \mathbf{v}\right)\right)\end{equation*}
\end{document}
